The growth of semiconductor III-V compounds by chemical vapor deposition (CVD), for example using organometallics and hydrides as elemental sources, has developed into a viable process with many potential commercial applications and has enabled significant control over the fabrication process. Group III-V semiconductor lasers have an important technological role (e.g., in optical fiber communications, medical equipment, CD players), and further growth of the use of such lasers can be confidently anticipated. One well-known compound semiconductor system is the (Al,Ga,In)P system. A compound belonging to the (Al,Ga,In)P system can have, for example, the general formula (AlxGa1-x)1-yInyP, where both x and y are between 0 and 1.Another well-known structures is the (Ga,ln)N system. A compound belonging to the (Ga,In)N system can have, for example, the general formula Ga1-yInyN, where y is between 0 and 1.
Semiconductor visible laser diodes (LDs) cover a wide spectrum of wavelengths. For example, the InGaN/GaN based LDs cover the violet to green spectrum (˜405-530 nm), and InGaP/InAlGaP system based LDs cover the red spectrum (635-690 nm). The wavelength from ˜530-635nm is not covered by any commercial LDs yet, which has some important applications in solid-state lighting, medicine, horticulture, displays, visible light communications (VLC) and in optical communication using plastic fibers. LDs in the green-yellow-orange range (530-635 nm) can be ideally grown either by InGaN/GaN or InGaP/InAIGaP based material system. For the InGaN/GaN quantum well (QW) structure, large strain and indium segregation prevent the growth of high quality light emitting devices in yellow and orange spectrum region. In the case of InGaP/InAIGaP system, small band offset between the quantum-well and barriers leads small carrier confinement and large carrier leakage prohibit the growth of high quality QW structures for yellow and orange emissions.
The only access to orange, yellow and green region has been achieved by frequency doubling of diode-pumped solid state lasers or infrared laser diodes or through the application of high external pressures which causes large blue-shifts of the emission wavelength of diode lasers. However, the frequency doubled diode-pumped semiconductor lasers uses non-linear crystal for inefficient second-harmonic generation and requires external distributed Bragg reflector and good heat sink which makes the overall system more complex. Though InGaN based vertical-external-cavity surface-emitting lasers which are also known as optically pumped semiconductor lasers are worthy contender for wavelength tuning, high optical output power and a nearly diffraction limited beam quality but electrical pumping in these devices are challenging. Also, the lasers produced by application of external pressure technique are non-practical for any commercial applications. Therefore, there is huge demand for replacements of these complex, expensive and power consuming lasers.
It is therefore an object of this disclosure to provide improved semiconductor laser diodes and methods of making and using such laser diodes with improved control over the emission wavelength.